The recently increased demand for portable electronic products such as laptop computers, video cameras, mobile phones, and so on, and the development of electric vehicles, energy storage batteries, robots, satellites, and so on started in earnest led into active researches on high-performance secondary batteries capable of repeated charging and discharging.
Currently, commercially available secondary batteries comprise nickel cadmium, nickel hydrogen, nickel zinc and lithium secondary batteries. Among them, lithium secondary batteries have drawn much attention because of little memory effect to allow unrestrained charging/discharging, as well as very low self-discharging rate and high energy density, compared to nickel-based secondary batteries.
For such secondary batteries, lithium-based oxides and carbon materials are mainly used as positive electrode active materials and negative electrode active materials respectively. A lithium secondary battery comprises an electrode assembly including a positive electrode plate and a negative electrode plate having positive electrode active material and negative electrode active material respectively coated thereon and intervened with a separator therebetween, and an exterior material, i.e., a battery case, which sealingly encases the electrode assembly along with an electrolyte.
Generally, lithium secondary batteries can be classified into a can-type secondary battery and a pouch-type secondary battery according to the shape of the exterior material, in which the can-type secondary battery integrates an electrode assembly into a metal can, and the pouch-type secondary battery integrates an electrode assembly into a pouch made of an aluminum laminate sheet.
Meanwhile, the secondary batteries have recently been widely used in medium- to large-sized devices such as automobiles and power storage devices as well as small-sized devices such as portable electronic appliance. Since the medium- to large-sized devices need high-capacity and/or high-power supply, such medium- to large-sized devices generally use a battery module instead of a single secondary battery, in which a plurality of secondary batteries are electrically connected. Specifically, such battery module generally includes a pouch-type secondary battery in order to facilitate stacking of a plurality of secondary batteries. Accordingly, the battery module may be regarded as an element in which a plurality of secondary batteries are connected in series and parallel in order to increase capacity and power.
Meanwhile, the pouch-type secondary battery has a shortcoming of weak physical strength and it is not suitable for stacking itself. As such, the pouch-type secondary battery is often used in such a form that is interposed between plates or inserted in a cartridge. Such plates or cartridge may form a predetermined shape (e.g., rectangular parallelepiped) to surround the exterior surface of the pouch-type secondary battery for protection of the pouch-type secondary battery or to allow easy stacking.
Meanwhile, considering mobility of the portable electronic appliance or electric vehicle, the secondary battery provided in the portable electronic appliance or electric vehicle is moved together when the portable electronic appliance or electric vehicle is moved. Such moving causes the secondary battery to move, and movement of the secondary battery can cause the secondary battery to be physically damaged by the adjacent components. For example, the pouch-type secondary battery may be damaged due to collision or friction with the plate covering the exterior surface of the pouch-type secondary battery, or with the cartridge in which the secondary battery is inserted. This can result in the exterior material of the pouch-type secondary battery, i.e., the pouch being peeled off or torn.
Such problem is mainly due to the clearance between the pouch-type secondary battery and the adjacent components. However, it is not easy to remove the clearance, and the presence of even a minute clearance can cause the problem mentioned above.